Vertical-cavity surface-emitting lasers (VCSELs) are useful for many applications including free-space and optical fiber telecommunications, optical interconnects, optical computing, optical recording and readout systems, and laser printers and scanners. For many of these applications, lasing action with a high beam quality and a high output power is required.
In the case of a single VCSEL device, a high beam quality requires a stable lateral mode of operation which is difficult to attain, especially as the lasing output power is increased or an operating temperature of the device is changed. In the case of an array of VCSELs, a coupling of the lasing action between individual VCSELs in the array primarily determines the beam quality and useful lasing output power (e.g. the amount of total output power that can be focused into a diffraction-limited spot or an optical fiber, or propagated over a distance). Attempts in the prior art to improve the beam quality and output power of VCSEL arrays have met with limited success. These prior-art attempts are largely based on evanescent coupling between adjacent VCSELs, and have further included laterally varying the reflectivity of a stack mirror forming the VCSEL array, or providing an optical element external to the VCSEL array for phase control (see, for example, U.S. Pat. Nos. 5,353,295 and 5,425,043 to Holonyak et al; U.S. Pat. No. 5,444,731 to Pfister; and U.S. Pat. No. 5,446,754 to Jewell et al).
An advantage of the vertical-cavity surface-emitting device of the present invention is that one or more vertical-cavity surface-emitting lasers (VCSELs) can be formed with a mode-control region having predetermined characteristics for defining and controlling a lateral mode for lasing within each VCSEL.
Another advantage of the present invention is that at least one pair of adjacent VCSELs can be formed with the mode-control region surrounding each VCSEL further acting to couple the lasing action between the pair of VCSELs, thereby providing a phase-locked operation characterized by the pair of VCSELs emitting laser beams which are substantially in phase with each other and therefore additive to form a single-lobed far-field output beam.
A further advantage of the present invention is that either index guided or index anti-guided operation of one or more VCSELs can be provided by adjusting one or more characteristics of the mode-control region either during epitaxial growth or thereafter.
Yet another advantage of the present invention is that the mode-control region which defines and controls a lasing mode within the VCSEL device can further act to channel an electrical current into a semiconductor light-emitting region of the device, thereby providing for efficient lasing action within the VCSEL device.
These and other advantages of the vertical-cavity surface-emitting laser device of the present invention will become evident to those skilled in the art upon examination of the following description, or can be learned by practice of the present invention.